The present invention relates to computer systems. More particularly, it relates to a power sequencing interface for peripheral units.
In computer systems, the principal part of the system is, of course, the central processor unit (CPU) wherein data is manipulated in accordance with programmed instructions. Such systems, however, also include a number of peripheral devices such as tape drive units, printers, and the like. Such peripherals are designed to be operated in conjunction with the central processor unit and, accordingly, must be controlled thereby. One feature of such a control is the initial power up sequence for energizing the peripheral units. In such systems, it is usual that a number of peripheral devices are controlled by a single unit identified as a peripheral controller. The peripheral controller is in turn controlled by the central processor unit. Again in such a system it is not unusual to have a number of such peripheral controllers each controlling a plurality of peripheral units. In an effort to standardize the interfacing between computers and the peripheral units, the United States Department of Commerce through its National Bureau of Standards has issued functional standards for the control units. In accordance with those standards each of the control units sequentially energizes the peripheral devices controlled thereby. In order to minimize power surges in the power supply system relating to the computer, the peripheral control units are energized sequentially.
Again, in an effort to standardize the functional relationship between the controlling computer and the peripheral controllers, the National Bureau of Standards has issued a further standard publication identified as Federal Information Processing Standards, Publication No. 61 (FIPS). That publication defines the standards against which the peripheral controlled sequencing interface structure is designed. Heretofore, the sequencing of the powering of the peripheral controllers through the power sequencer interface unit has been accomplished by such means as stepping switches and power relays. Each of these types of units requires considerable power consumption and space and provides a noisy environment.